BATON ROUGE, La. » It would have been easy to mistake what was happening in a hotel ballroom here for a religious service. All the things that might be associated with one were present Sunday: 80 people drawn by a common conviction. Exhortations to service. Singing and light swaying. An impassioned sermon.

There was just no mention of God.

Billed as Louisiana’s first atheist service and titled "Joie de Vivre: To Delight in Being Alive," it was presided over by Jerry DeWitt, a small, charismatic man dressed all in black with slick, shiny hair.

"Oh, it’s going to be so hard to not say, ‘Can I get an amen?’" he said with a smile, warning people that this was going to be more like church than they might expect. "I want you to feel comfortable singing. And I want you to feel comfortable clapping your hands. I’m going to ask you to silence your cellphones, but I’m not going ask you to turn them off. Because I want you to post."

As DeWitt paced back and forth, speaking with a thick Southern accent, his breathy yet powerful voice occasionally cracked with emotion. The term may be a contradiction, but he is impossible to describe as anything but an atheist preacher.

DeWitt acts so much like a clergyman because he was one.

He was raised Pentecostal in DeRidder, La., a small town near the Texas border. In 2011, after 25 years as a preacher, he realized he had lost all connection to the religious point of view that had defined most of his life. He left the church and found himself ostracized in his hometown and from his family. Since then, DeWitt, 43, has become a prominent advocate of atheism, giving lectures around the region and providing an emotional counterpoint to more academic atheist exponents like Richard Dawkins and Christopher Hitchens.

With Sunday’s service – marking the start of Community Mission Chapel in Lake Charles, which DeWitt called a full-fledged atheist "church" – he wanted to bring some of the things that he had learned from his years as a religious leader to atheists in southern Louisiana.

The percentage of religiously unaffiliated Americans appears to be on the rise. A 2012 Pew Research Center study found that while only about 6 percent identified as atheist or agnostic, they were among nearly 20 percent classified as religiously unaffiliated. That was up from 15 percent in 2007, a greater increase than for any traditional faith.

DeWitt counts himself among the hard-line atheists, but he believes something may be lost when someone leaves the church – not just the parts about God, but also a sense of community and a connection to emotion.

"There are many people that even though they come to this realization, they miss the way the church works in a way that very few other communities can duplicate," he said in a phone interview. "The secular can learn that just because we value critical thinking and the scientific method, that doesn’t mean we suddenly become disembodied and we can no longer benefit from our emotional lives."

Some in the audience had a difficult time coming to atheism. Joshua Hammers, a member of an atheist organization in Lake Charles, said he had been completely separated from his community and social life when he left the Pentecostal church in which he was raised. For him, there was something comfortable, a reminder of childhood, about hearing DeWitt preach.

"We were at the Reason on the Bayou conference, and everything else was just like a lecture," Hammers said, referring to a secular rally held in April at Louisiana State University. "Then Jerry got up, and he was just, you know, preaching the message. Most other atheist leaders are academics and intellectuals, and Jerry’s not like that. He’s just talking to your heart."

Services are gaining traction as outlets for organized atheism in places like London, Houston, Sacramento and New York, as well as at universities with humanist chaplains. In a deeply conservative region like the Deep South, they can serve a vital purpose: providing a sense of camaraderie in what many have found to be a hostile environment for nonreligious people.

"Here, we have a very strong sense of community," said Russell Rush, a former youth pastor from DeRidder. "When you go into an actual church, it’s almost like having a family reunion. When you leave that lifestyle, and leave that church life behind, a lot of times you can feel ostracized. Things like this let fellow atheists and agnostics know that they’re not alone."

DeWitt sees services like his as giving a human shape to a broad intellectual movement that is in its infancy. He believes that he and the others in the room are building something meant to last.

"Though this movement has had starts and stops throughout world history, right now it’s important to remember that we are young," he said after a singalong to a song of that name by the band Fun. "Someday, what you are doing will become normal. Isn’t that a feeling?"

© 2013 The New York Times Company